This invention relates to the production of rigid polyisocyanurate or polyurethane foam materials used in the building materials trade. In particular this invention relates to the production of rigid foam materials manufactured from the reaction of polyols and isocyanates generally and specifically to reactants that contain additives capable of modifying the form of the resultant product to produce fine cell structures which are desirable to have in the finished product.
Specifically, compounds acting as surfactants and/or emulsifiers have been extensively investigated for use in the production of uniform cell polyurethane foam materials, both rigid and flexible, and many non-ionic types of compounds or mixtures therewith have been employed. U.S. Pat. No. 4,207,410 at Column 5, lines 45, et. seq., lists several non-ionic material having utility for modifying cell uniformity and size.
It is generally believed that surfactants, and preferably silicone based surfactant compositions, have the ability to stabilize the bubbles formed during the polymerization reaction. Without a suitable surfactant, the bubbles would progressively get larger resulting in a very coarse, open celled foam structure with poor thermal conductivity properties.
The non-ionic surfactants useful in this process can generally be characterized as water-in-oil emulsifiers which assist in the mixing of the lipophilic isocyanate and the hydrophilic polyol. It is also desirable to utilize surfactants that do not react deleteriously with either of these reactants in the polymerization reaction.
Since some surfactants of the water-in-oil variety contain reactive OH groups or can be classified as polyols themselves, these would normally be considered unsuitable candidates for selection to achieve the desired results. U.S. Pat. No. 4,160,076 describes several classes of materials which react with isocyanates suitable for the manufacture of polyurethane foam which themselves can be characterized as non-ionic surfactants. Also some of the materials disclosed in that patent were useful only for the production of large cells in a soft sponge-like foam.
Other patents describing typical polyol-isocyanate reaction mixtures included U.S. Pat. Nos. 3,833,526; 3,703,849; and 3,579,471. The reference literature often referenced is Saunders, J. H. and Frisch, K. C., Polyurethanes Chemistry and Technology, Part I. Chemistry, Interscience Publishers, 1963, pg. 244, and Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 19, pp. 531, 532, 553; 554 and Table 22 (2nd Ed.); and Schonfeldt, Surface Active Ethylene Oxide Adducts, pp. 227-230, (Pergamon Press, 1969); and W. C. Griffin, Clues to Surfactant Selection Offered by the HLB System Symposium on Surfactants, Official Digest, June 1956, pp 446-455.
It can be seen from the descriptions contained in the foregoing that it is important to provide the polyol and the isocyanate mixture with an emulsifier or surfactant that will have an appropriate affinity for both the hydrophilic polyol and the lipophilic isocyanate in order to obtain a uniform distribution of the reactants for the production of a foamed polyurethane product. Many of the currently employed surfactants, particularly the silicone based compounds, while suitable for this function are quite costly and therefore a substitute has been sought which would accomplish the same function.